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News Article

Invasive tree species threatens biodiversity hotspot

Programme of intervention is needed to prevent loss of endemic species

While non-native plants invade some tropical forests, few long-term studies of their invasions exist. An invasive Australian Tree, known locally as “mock orange”, is threatening many rare and endangered species, including birds, butterflies and orchids, in the forests of Jamaica’s Blue and John Crow Mountains National Park.  The species, Pittosporum undulatum, was introduced to a botanic garden in the Blue Mountains during the late 19th Century. In a new study published in Biological Conservation, researchers recommend an urgent program of control for the species.

The tree, as its local name suggests, has glossy, fast-growing leaves with bright orange fruit which contains small, sticky, sugary-coated seeds.  These seeds are dispersed by native Jamaican birds and they have been invading habitats at a high rate.  The species started to inhabit land that had been abandoned from the cultivation of coffee and tree crops, although more recently it has extended into the natural forests of the Blue and John Crow Mountains National Park.  Since then, the invasion of the trees has been accelerated by forest damage caused by Hurricane Gilbert in 1988 and is likely to be further exacerbated by future hurricanes.   

Researchers studied the forests over a 40 year period and noticed a continuous increase in the abundance of the invasive tree, which now accounts for more than 10% of all tree stems.  The research predicts that the threat posed to the biodiversity hotspot of the Jamaican Blue Mountains will increase.  This will occur particularly after the next hurricane severely damages the forest canopy.  

Study co-author John Healey, explains that, "over the past 24 years the severity of this invasion was associated with a decline in the diversity of native tree species, including those species that are found only in Jamaica, which are the highest conservation priority. The 'mock orange' grows faster than most native trees, and its dense foliage casts a dark shade over their seedlings, severely restricting their regeneration."

If remedial action is taken now, conservation measures could help avoid a biodiversity catastrophe in Jamaica as well as many other global biodiversity hotspots that are threatened by invasive species.  However, this is being hindered by a lack of available resources.

Study lead Peter Bellingham made the following request: "Given the strength of our evidence of the serious consequences of this invasion for biodiversity, we urge the relevant institutions in Jamaica, and international funding bodies, to prioritise a programme of control of this species. We are sure that active intervention at this stage would be very cost effective, reducing the much greater costs of trying to restore the native forests if the invasion is allowed to spread further."

The study is a collaboration between Landcare Research in New Zealand as well as the Universities of Bangor (UK), Cambridge (UK) and Denver (US).

Subscribers of the Forest Science database can access further information on this topic.  For example, using the search string "Pittosporum undulatum" AND ("invasive species" or "introduced species") yields 28 records, while "tropical forest" AND biodiversity AND ("invasive species" or "introduced species") gives 115 results.  A selection of these is provided in the further reading section below.

Also, further information on invasive species is available on the CABI open access Invasive Species Compendium.   Specifically, there is a datasheet on Pittosporum undulatum.

Journal Reference:

Peter J. Bellingham, Edmund V.J. Tanner, Patrick H. Martin, John R. Healey, Olivia R. Burge. Endemic trees in a tropical biodiversity hotspot imperilled by an invasive treeBiological Conservation, 2018; 217: 47 DOI: 10.1016/j.biocon.2017.10.028

Article details

  • Author(s)
  • Stephanie Cole
  • Date
  • 17 January 2018
  • Source
  • Bangor University
  • Subject(s)
  • Environment
  • Forest trees